1. Field of the Invention
The present invention relates to a hinge device for a casing.
2. Description of the Related Art
A hinge device is widely used to combine two parts that are rotatable with respect to each other. A hinge device suitable for combining a computer monitor with a stand that supports the monitor to be rotatable with respect to each other. The hinge device includes a shaft portion 10, a supporter 20, and springs 30.
The shaft portion 10 includes a flange 11 and a shaft 12 and a fixing portion 13 provided on both sides of the flange 11. The shaft 12 includes a circular section 12a adjacent to the flange 11 and a combining portion 12b extended from the circular section 12a and processed to have a non-circular section. The fixing portion 13 is fixed to either a monitor or a stand.
The supporter 20 through which the circular section 12a of the shaft 12 is inserted includes a fixing portion 22 to be fixed to either the monitor or the stand and a restrain projection 23.
The springs 30 which are all convex belleville springs are elastically transformed in a longitudinal direction of the shaft 12 by a nut 40 which combines with the shaft 12. As mentioned above, the elastically transformed springs 30 apply an elastic force on the supporter 20 to the flange 11 of the shaft portion 10. Accordingly, frictional torque for suppressing the rotation of the supporter 20 with respect to the shaft portion 10 by a force is generated between the shaft portion 10 and the supporting portion 20.
Washers 50 and 60 having holes 51 and 61 for receiving oil lubricant are installed on both sides of the supporting portion 20. A stopper 70 having a combining hole 71 and a stopper protrusion 72 is installed between the spring 30 and the nut 40. The combining hole 71 has an opening corresponding to the combining portion 12b so that the rotation of the stopper 70 with respect to the shaft portion 10 can be prevented.
In the hinge device, the supporting portion 20 can rotate with respect to the shaft portion 10 only when a torque larger than the frictional torque provided by the springs 30 is applied between the shaft portion 10 and the supporting portion 20. Therefore, for example, when the supporting portion 20 is fixed to the monitor and the shaft portion 10 is fixed to the stand, it is possible to prevent the supporting portion 20 from arbitrarily rotating together with the monitor by the weight of the monitor. When the supporting portion 20 is rotated with respect to the shaft portion 10 by applying a torque larger than the frictional torque, the rotation is performed smoothly due to the oil lubricant in the through holes 51 and 61. When the supporting portion 20 rotates by a predetermined degree with respect to the shaft portion 10, as shown in FIG. 3 by the dashed line, the stopper protrusion 72 is caught in the restrain projection 23. Thus, further rotation is prevented.
In a conventional hinge device having the above structure, washers having through holes are provided on both sides of the supporting portion so that the rotation of the supporting portion with respect to the shaft is performed smoothly and the oil lubricant is received in the through holes of the washers. Therefore, the overall structure and assembly process becomes complicated due to the washers.